Case-hardening material.



' No Drawing.

HUGH RODMAN, OF PITTSBUBG, PENNSYLVANIA.

CASE-HARDENING MATERIAL.

To all whom it may concern:

I Be it known that I, HUGH RoDMAN, a citizen of the United States, and a resident of Pittsburg, in the county of Allegheny and State of Pennsylvania, have made a new and useful Invention in Case-Hardening Material, of which the following is a specification. This invention, relates to material for use in cementing or case hardening.

Cementation or case-hardening by dry packing has hitherto, so far as-I amaware,

involved the use of more or less costly carbonaceous material such as bone dust or powdered charcoal, used alone or mixed with soda-ash or lime. Cementing or case hardening by dry packing is usually carried out by packing the articles to be treating in the cementing or case-hardening material in closed castiron or clay pots, which are externally heated at a temperature varying from 14:00 to 2000 Fahrenheit for-from a few hours to a few days.

So far as I know the action of the cement ing or case-hardening material is not well understood, but carbon from the material is absorbed by the articles treated and it has been thought that the action of the bone dust or powdered charcoal is accelerated or intensified by adding to these materials such substances as lime or sodium carbonate. I have found that coke, acomparatively pure and cheap form of carbon, which in itself has practically no casehardening properties, can be rendered active as a cementing or case-hardening material'by adding thereto an energizing substance for examplejime, sodium hydrate or soda-ash and I have found in use that such material does not mar or pit the surface of the metal articles or parts treated. By,ener,gizing substance, I mean such material, not necessarily cafbonaceous material, as will when added to an inactive carbonaceous substance, render such carbonaceous substance active, as a carbonizing agent. Various mixtures of coke and these energizing substances may be used, but I Specification of Letters Patent.

Patented Feb. 15, 31910.

Application filed May 15, 1909. Serial No. 496,271.

find that excellent results may be obtained from a mixture of 100 parts by weight of coke granules, -about 11- inch diameter, '15 parts of finely powdered sodaash and 10 parts of finely powdered slaked lime. I prefer to mix these materials by first adding to the coke granules su fficient oil (preferably a heavy hydro-carbon oil) to cover the surface of the granules and then to, add the powdered soda-ash and lime, stirring it so that the powdered soda-ash and lime will adhere to the coke granules.

I find that the material is improved somewhat as a commercial product by the addition of the oil, for a thorough admixture of the constituents of the material is thus maintained.

It is necessary that the cementing material should not pit or mar the surface of the metal parts treated and I have found that in order to preserve a good surface on the metal parts it is essential that in selecting the energizing substances those evolving harmful substances such as fluorin must be avoided. r

Having thus described my invention, what I claim is:

1. Cementing or case hardening material containing coke and energizing substance which will maintain-a smooth surface on the metal parts to be treated.

2.'Cementing or case hardening material .containing coke and soda ash.

consistingessentially of coke and soda ash.

Intestimony whereof, I have hereunto subscribed my name this 12th day of May,

HUGH RODMAN. Vitnesses C. W. MoGnnn, GEO. O. WALKER. 

